diff --git a/ipv6/in.cidr b/ipv6/in.cidr
index 8727ed2b5..a75c55a7f 100644
--- a/ipv6/in.cidr
+++ b/ipv6/in.cidr
@@ -826,6 +826,7 @@
 2001:df3:4a40::/48
 2001:df3:4c40::/48
 2001:df3:4f40::/48
+2001:df3:4fc0::/48
 2001:df3:5000::/48
 2001:df3:5780::/48
 2001:df3:5880::/48